Hydraulic motor

ABSTRACT

A hydraulic motor of the radial piston type characterized in the provision of a housing having a plurality of radially extending cylinders in which pistons are radially reciprocable, said pistons being linked to the crankpin of a crankshaft journaled in said housing, and being successively communicated by valve means operated in timed relation to the rotation of the crankshaft with inlet and outlet ports of said housing so that during the power stroke of each piston, a succeeding piston is simultaneously communicated with the inlet port so as to produce a toggle joint force at the crankpin to provide a motor having increased torque and efficiency. The hydraulic motor herein is further characterized in that it has at least three equally spaced apart radial pistons linked to the crankpin of the crankshaft whereby, during rotation of the crankshaft, toggle joints as aforesaid are successively defined by the crankpin and the connecting rods of the first and second pistons, the second and third pistons, and the third and first pistons. The hydraulic motor herein is still further characterized in that the toggle joint force aforesaid at the crankpin for driving the crankshaft is initiated prior to the trailing piston reaching its top dead center position at which time it is pressurized and is continued until the leading pressurized piston has passed its bottom dead center position at which time pressure thereon is released to the outlet port.

United States Patent n91 Purcell I HYDRAULIC MoToR Howard M. Purcell, 2127 S. Bclvoir Blvd, South Euclid. Ohio 4412i l7o| Inventor:

I5Z| .8. (Tl. i i t v A i 9l/48l I5] I Int. Cl A t i t i F0") 3/lll Field Ol Search i A Jl/4Xl, 496. 6.5 49l [56] References Cited UNlTED STATES PATENTS 2.088.583 il/ILW Bishop it Jl/4Xl 2,3)7.l3[l 1/1940 Dawson it Jl/49h 2.700.411 5/W55 Bray. )l/48l 2 )-l5.-l5l 7/[Wvll (iriswot '-)|/49l .UNHUM 5mm} Sttner v A i t i t i. 91/498 il7) (llo 4/Wo5 l'horton l runp.. )l/4Hl ijs mot IZ/Wm Host-Ii i. QIMXS RJHJO) o/Wh? Manselln 9|/(1.5 77| -lll lZ/lfill Hytlc i t t i i. a l/6.5

Primary litumimr-William L. Freeh ,lrmrm- Agent. or l"z'r'/n-Donnelly, Maky, Renner 62 (Hm I 7 l ABSTRAUI' A hydraulic motor of the radial piston type character- Apr. 1,1975

ized in the provision of a housing having a plurality of radially extending cylinders in which pistons are radially reciprocable, said pistons being linked to the crankpin of a crankshaft journaled in said housing, and being successively communicated by valve means operated in timed relation to the rotation of the crankshaft with inlet and outlet ports of said housing so that during the power stroke of each piston, a succeeding piston is simultaneously communicated with the inlet port so as to produce a toggle joint force at the crankpin to provide a motor having increased torque and efficiency The hydraulic motor herein is further characterized in that it has at least three equally spaced apart radial pistons linked to the crankpin ot the crankshaft whereby. during rotation of the crankshaft. toggle joints as aforesaid are successively defined by the crankpin and the connecting rods of the first and second pistons, the second and third pistons, and the third and first pistons. The hydraulic motor herein is still further characterized in that the toggle joint lorce aforesaid at the crankpin for driving the crankshaft is initiated prior to the trailing piston reaching its top dead center position at which time it is pressurized and is continued until the leading pressurized piston has passed its bottom dead center position at which time pressure thereon is released to the outlet port.

4 Claims, 8 Drawing Figures PATENTEU APR 1 I975 SHEET 1 If 3 P'Aremw Hers SFEU 2 6F 3 PMENIED H975 3.874.270 sum 3 g 3 I80 4 DEGR E E5 ROTATION 4'07 3 300- 5 z 350- A r53 320- 1 I10 I I 0- 00' new IBO' a40- sooaeo- DEGRE ES ROTATION HYDRAULIC MOTOR BACKGROUND ()I 'l'Hl-l INVENTION Radial piston hydraulic motors generally comprise a cylinder block carrying pistons which are urged radialiy outwardly by fluid pressure into engagement with a surrounding stator thus to cause rotation of the cylinder block and its output shaft. the cylinder block being provided with a rotating valve member to alternately conduct fluid under pressure to the outwardly moving pistons and to exhaust fluid from the inwardly moving pistons. It is also known to provide a radial piston hydraulic motor in which the pistons are actuated radially inwardly. said pistons being connected to rocker arms having arcuate shoes engaged with a rotatable eccentric. and again. fluid flow into and from the radially outer ends of the cylinders is controlled by a rotating valve member.

SUMMARY OF THE INVENTION In contradistinction to known types of radial piston hydraulic motors, the hydraulic motor herein comprises a housing having a plurality of radially reciprocable and linked to the crankpin of a single throw crankshaft journaled in said housing: and valve means operated in timed relation to the rotation of the crankshaft so that said pistons are successively communicated with inlet and outlet ports in the housing and so that. during the power stroke of each pistom a succeeding piston is simultaneously communicated with the inlet port to form a toggle joint in which a toggle force at the crankpin increases the motor torque and efficiency.

It is a principal object of this invention to provide a highly efficient radial piston hydraulic motor which is of simple construction for economy of manufacture and assembly.

It is another object of this invention to provide a radial piston hydraulic motor of the character indicated in which the togle joint driving action on the crankpin of the motor crankshaft to which the pistons are linked commences prior to the trailing piston reaching its top dead center position and continues until the leading piston has passed its bottom dead center position,

Other objects and advantages will appear from the ensuing description BRIEF DESCRIPTION OF THE DRAWING FIG. I is a central vertical cross-section view passing diametrically through the motor housing;

FIGS. 2. 3 and 4 are cross-section views taken along the lines 2-2 and 3-3. FIG. I and line 44. FIG. 3;

FIGS, 5 and 6 are typical displacement and torque curves of a hydraulic motor embodying the present invention; and

FIGS. 7 and 8 schematically illustrate the starting and finishing positions of the toggle joint action obtained by simultaneous pressurization of two successive pistons.

DETAILED DI'ISCRIP'IION OF A PREFERRED EMBODIMENT The hydraulic motor I herein comprises housing parts 2 and 3 clamped together as by screws 4 and forming a crankcase having hearings 5:5 therein. such as the self-aligning spherical roller bearings shown in FIG. I. for rotatably supporting the crankshaft 6 therein for rotation about its oppositely extending shaft portions 7 and 8 of which the shaft portion 7 extends through the housing part 2 and bearing 5 to constitute the output shaft of the motor I and of which the shaft portion 8 extends through bearing 5 into a bore 9 of the housing part 3 and has affixed thereto a valve operating cam III. The crankshaft 6 has thereon a counterweight II and a flywheel l2. A retainer plate I4 is bolted to the housing part 2 to retain a seal assembly I5 around the output shaft portion 7. A suitable mounting bracket I6 may be secured to the housing part as shown.

The housing part 2 is formed with three threaded openings 17 which are equally spaced circumferentially around the housing part 2 and which are axially offset with respect to each other as best shown in FIG. I. Screwed into said openings l7 are the respecthe cylinder assemblies l8. each of which comprises an outer part I) in which a piston 20 is reciproeable and an inner part 2] which has an enlarged bore 23 for radially slidably receiving a guide sleeve 24 which carries the wrist pin 25 to which the connecting rod 26 and piston 20 are connected as shown in FIGS. I and 2. the other ends of the connecting rods 26 being connected to the crankpin 27 of the crankpin 6 in side by side relation.

The housing part 3 has a pressure inlet port 28 which communicates with an annular inlet chamber 29 which is closed by a cover plate 30 which is secured to the housing part 3 as shown by the screws 3|. said cover plate 30 also closing the bore 9. The housing part 3 also has a return port 32 adapted for communication with a fluid reservoir (not shown). said return port 32 having a passage 34 which opens into the cylindrical chamber 35 defined between the housing parts 2 and 3 so that the chamber 35 will be approximately one half full of hydraulic oil for lubricating the crankpin 27, the bearings 5, the cam I0. etc.

The housing part 3 also has a passage 36 therethrough which communicates with the chamber 35 above the return passage 34. said passage 36 intersecting the pressure inlet passage 28 and having therein a relief valve 37 to prevent build up of excess pressure in the inlet passage 28, the outfall side of said relief valve 37 being communicated with the oil reservoir (not shown). and the spring biased relief valve member 38 having an opening therethrough for return flow to the reservoir in the event that the level of oil in the chamber 35 rises above the return passage 34. When the spring biased relief valve member 38 is moved away from its seat. the excess fluid pressure is relieved and conducted to the reservoir through the relief valve member 38 and to the return passage and port 34 and 32 via the chamber 35.

The housing part 3 has three equally spaced apart radially disposed bores 40 which intersect the annular pressure chamber 29 and the return chamber 4| within bore 9 in which the cam It) is disposed and in each ra dial bore 40 is a valve assembly 42 including a valve member 43 which constitutes a cam follower biased by spring 45 to maintain its cam follower bearing 46 in engagement with the surface of cam I0. The radially inner end of each valve member 43 is slotted as shown to straddle the opposite sides of the cam 10 to prevent rotation of the valve member 43 thus to maintain the surface of the cam follower hearing 46 parallel to the axis of the crankshaft 6. The valve member 43 is of pressure balanced construction provided with a peripheral groove 47 which. when the respective valve mem bers 43 are moved by the cam I0 radially outward as shown by the lower valve members 43 in FIG. 3. opens communication hetwecn the pressure cltanther 2) and the radially ottter ends of the respecti e cylinder parts l) by way of the conduit and lilting means 48 and w hich when in the closed position as represented hy llte \al\c ntenther 43 at tlte top in l-l(i 3 opens conr munication hctween tlte ottter end of tlte associated cylinder part I) witlt tlte retttrn chanther 4| \ia tlte conduit and fitting tneatts 48 and tlte cetttral hore 4') of the associated closed \al\e ntenther 43.

hi the illustrated emhodiment of the hydraulic ntotor herein the pistons 20 are of one-half inch diantcter attd ha\e a stroke of I; ineltes and tlte L/R ratio ol'the cottnecting rod length to the crankpin radius is ahout 3. l l. In the operation of the hydraulic ntotor it is preferred to employ a pressure system ha\ing an accumulator therein to ntaintain a sullstantially cottstant ittlet pressure to the motor I w hiclt together with the flywheel 12 are el'fecti e to pro\ide aterage displacentettt and torque \alttes as denoted hy tlte lines 52 and 53 iii HUS 5 and h.

In the presettt case the surface of cattt 10 is so fornted that as the crankshaft (1 is tlri\en iii the direction indicated hy the arrow in Fl( i. 3. caclt rahe ntenther 43 remains itt open position for pressuri/ing its associated piston 20 for more tltatt 1N0 rotatiott of the cranksltaft (x hoth prior to and after the rcspecti\c top and hotlttltt dead center positions of tlte crankpin 27 witlt respect to the associated piston 20, and hence oil i displaced front each piston 20 during rotation to and frottt said dead center positions either tltrouglt the opett \al e ntenther 43 or through the associated check \al e 5| which perntits tlte thus displaced oil to flow to the pressure ittlct chamber 2) iii the e ent that the \ahe tttcltt her 43 is itt alt ittterntediate position closing communi cation with hotlt the inlet and return ports 28 attd 32.

In tltc arrangentettt shown itt single cattt It) operates all of the ahc menthers 43 and by reason of the shaping of the cam sttrfaee of cam 10 as aforesaid. the pistotts 20 are pressuri/etl in sequence with two suceessi e pistons 20 heing operati\e to dri\e the crankshaft 6 with the assistance of a toggle force as clearly shown itt l-l( i3 7 and 8. ll(ii 7 shows the cottttectittg rods 26 of two sucee sne pistons in their positions at the heginning of the toggle actiott as the trailing piston 2|) at the top approaches its top dead center position. and Fl(i, 8 shows the satne two connecting rods 26 in their positions at tltc end of the toggle action after the leading piston 20 at the left has passed its hottom dead center position.

As e\ ident. when two sttecessite pistons 20 are pressttl't/cd as shown in FIGS. 7 attd 8. the connecting rods 26 and crattkpin 27 form a toggle joint itt which the tog gle force l Zl-"HHA. In the specific eltthotlitttcttt of the in\ention lterein shown and descrihed the \al e menther 43 for the upper piston 20 is opetted to inlet presure when the crankpin 27 is altout 13 itt ad ance of it top dead cettter position ll 'ltir 7) and the \al\e ntenther 43 for the left piston 20 pressuri/cs the latter until the crankpin 27 is about 35 past hottont dead eetttet' position tl"l(i. lilv .\s the crankshaft it rotates from the l-'l(i, '7 to the l-'l(ii 8 position. the net torque itt clockwise direction increases attd decreases according to the relationship 9 PB 1 l"( 'll). (lockwise rotation of the crankshaft (I heyond the FIG. 8 position operates the tah e ntem her 43 for the left piston 20 to communicate the same with the teturn port 32 attd at the position of the cranklyll pin 27 about 25 hetore the top dead center position with respect to the piston 20 at the right. the \ahe ntenther 43 therefor is operated to close communica tion with the return port 32. At thi stage there may he ahont a I" rotation of the crattkpin 27 hcfore the rigltt piston 20 is cotnnttmieated with the inlet port 28. ie w hen the crankpin 27 is ahotlt Z3" hefore the top dead center position with respect to the piston 20 at the right t'ntil that time the crankshaft 6 is dri\en hy the top pressuri/ed piston 20. When the top and right pistons 20 are thus pressuri/ed the toggle action is re peated as already descrihed ilt comtection with FIGS, 7 and 8 whereby the top piston 20 hecomes the leading tor lel'tt piston 20 in l"l(i. 7 and the right piston 20 liccomes the top trailing t top) piston 20 in l-'l(i, 7. Finally. the left and rigltt pistons 20 form a third toggle ioint and as the rotation of the erankshaft (i continues. the toggle joint action of FIGS. 7 attd 8 is repeated.

'lhe cttthodintents of the imention in which an eyclusi\e property or prhilegc is claimed are defined as follows:

I. A hydraulic motor comprising a housing hating inlet attd outlet passages and ha\ ing a plurality of radially e\tettdittg cylinders; a crankshaft iournaled in said housing having a erankpin; pistons reciprocahle in the respecth e cy lindcrs attd ha ing connecting rods littking the respective pistons to said crankpin1 \ahe means uperated in timed relation to rotation of said crankshaft to successnely communicate the radially outer end portion of each cylinder with said inlet and outlet passages with overlap of the contntuttication of one cylinder and a succeeding cylinder with said inlet passage to produce a toggle force at said crankpin for increased motor torque and efficiency: said al\c means communicating the radially outer end portion of one cylinder with said inlet passage prior to attd after said crankpin reaches top dead center position thereof and communicates the radially outer end portion of a preceding cylinder with said inlet passage until said erankpin passes hottont dead center position thereof w hcrehy a toggle force is imposed on said crankpin during the overlap of the communication ofsaid one and preceding cylinders with said inlet passage.

2. The motor of claim I wherein said housing has at least three equally spaced apart cylinders with the pistons therein linked by the respecti e connecting rods to said crankpin: and wherein said \ahe means effects o erlap as aforesaid of the conmtunication of each cylinder attd a succeeding cylinder with said inlet passage wherehy suceessi e toggle forces are produced at said crankpin during rotation of said crankshaft 3. 'l'he motor of claim I wherein said valve means comprises \al\e tttenthers mtwahle in said housing to selectively communicate said inlet and outlet passages with the respeethe cylinders; wherein a cam on said crankshaft aetuates said \al e ntenthers in sequence as aforesaid; w herein each al\e ntenther. in an intermediate position. closes communication of its cylinder with said otttlct passage hel'ore communication is opened between said cylinder and said inlet passage while the piston therein is aiming radially outwardly; and w herein a clteek \al e hetwecn each cylinder and said inlet passage permits fluid flow front said cylinder to said inlet passage in such intermediate position of said yalte ntenther.

4. The hydraulic motor ofclaittt I wherein each eylittdcl has a radially enlarged hore itt which a gttide slee\ e of diameter greater than aid piston is reciprocahle; said guide slee e carrying a w ristpin to which the radially inner end of the associated pi ton and the radially ottter end ot'tlte associated connecttng rod are con neetetl 

1. A hydraulic motor comprising a housing having inlet and outlet passages and having a plurality of radially extending cylinders; a crankshaft journaled in said housing having a crankpin; pistons reciprocable in the respective cylinders and having connecting rods linking the respective pistons to said crankpin; valve means operated in timed relation to rotation of said crankshaft to successively communicate the radially outer end portion of each cylinder with said inlet and outlet passages with overlap of the communication of one cylinder and a succeeding cylinder with said inlet passage to produce a toggle force at said crankpin for increased motor torque and efficiency; said valve means communicating the radially outer end portion of one cylinder with said inlet passage prior to and after said crankpin reaches top dead center position thereof and communicates the radially outer end portion of a preceding cylinder with said inlet passage until said crankpin passes bottom dead center position thereof whereby a toggle force is imposed on said crankpin during the overlap of the communication of said one and preceding cylinders with said inlet passage.
 2. The motor of claim 1 wherein said housing has at least three equally spaced apart cylinders with the pistons therein linked by the respective connecting rods to said crankpin; and wherein said valve means effects overlap as aforesaid of the communication of each cylinder and a succeeding cylinder with said inlet passage whereby successive toggle forces are produced at said crankpin during rotation of said crankshaft.
 3. The motor of claim 1 wherein said valve means comprises valve members movable in said housing to selectively communicate said inlet and outlet passages with the respective cylinders; wherein a cam on said crankshaft actuates said valve members in sequence as aforesaid; wherein each valve member, in an intermediate position, closes communication of its cylinder with said outlet passage before communication is opened between said cylinder and said inlet passage while the piston therein is moving radially outwardly; and wherein a check valve between each cylinder and said inlet passage permits fluid flow from said cylinder to said inlet passage in such intermediate position of said valve member.
 4. The hydraulic motor of claim 1 wherein each cylinder has a radially enlarged bore in which a guide sleeve of diameter greater than said piston is reciprocable; said guide sleeve carrying a wristpin to which the radially inner end of the associated piston and the radially outer end of the associated connecting rod Are connected. 